The invention relates to an air transfer system, and more particularly to an air transfer system for a shell press having a blanking and forming die station and a curling die station commonly operated therein.
Beverage cans, food cans and the like have a can body and separately manufactured ends, which are called shells that are sealed to the can body. Generally, the shells are manufactured from sheet steel, aluminum, or other acceptable material in a series of presses, wherein the shell is blanked and formed in one press and then transported to a second press which curls the edges of the blanked and formed shell. The uncurled shell has a peripheral edge that is generally perpendicularly disposed to the main body of the shell, and, before the shell is stacked and then sealed to the beverage can it must first be curled at its peripheral edge and then coated with a sealant which forms a resilient gasket against the can body.
A major problem currently existing in the industry is directly related to the use of separate presses to blank and form the shell and to curl the shell. Depending upon the layout of the manufacturing plant, the blanked and formed shells may first have to be stacked one upon the other and then transported to the curling die station to be curled, or the situation may arise wherein it is necessary to store stacked blanked and formed shells due to unforeseen circumstances, for example, an inoperable curler. In any event, the shapes of the blanked and formed shells permit them to be conveniently stacked since one shell tightly nests within another. However, because the blanked and formed shells tightly nest one upon the other, it is virtually impossible to mechanically cut an individual shell from a tightly nested stack of shells. This requires the shells to be stored in an unstacked state, which requires considerable space and is time consuming, costly and inefficient.
In some shell press installations, the blanking and forming die station and curling die station are in close proximity with one another so that the blanked and formed shells may be transported to the curling die station, for example, by use of a conveyor assembly. The shells are generally blanked and formed from the strip stock in groups of twelve, fourteen, or sixteen. For example, a group of sixteen may be blanked and formed from the strip stock in two rows of eight, which rows are staggered relative to each other to minimize the strip stock skeleton remaining after the blanking and forming operation. Since it is not practical to stack the blanked and formed shells, it is necessary to keep them separated from each other between the blanking and forming die station and curling die station.
A typical prior art embodiment of the above shell press installation comprises a double acting press that blanks and forms the shells, a ring curler for curling the blanked and formed shells, and a conveyor assembly extending therebetween. The blanked and formed shells may be delivered to the conveyor assembly in one of two common ways. The blanking and forming shell press may be designed to tilt towards the conveyor assembly so that the blanked and formed shells slide from the press onto the conveyor for conveyance to the ring curler, or a mechanical kicker-type device may be used with a stationary blanking and forming shell press to eject the blanked and formed shells onto the conveyor. In this particular embodiment, the ring curler generally comprises two rotating rollers between which the shells pass to be curled.
Although the above embodiment permits the blanking and forming operation and the curling operation to be performed in close proximity to each other, certain problems and disadvantages exist such as the requirement for additional space for the conveyor assembly, frequent denting of shells by the kicker device in ejecting the shells onto the conveyor assembly, and the tendency of the ring curler to produce shells having nonuniform curled edges.
Another typical prior art embodiment, which may be a modification of the above described embodiment, use a die curler in place of the ring curler. Here the blanked and formed shell is curled at a die station, which is commonly housed in a press separate from the blanking and forming shell press and operated independently thereof. The distance between the blanking and forming shell press and the die curler may be such that a conveyor assembly may be used to transport blanked and formed shells to the die curler. Stacking for transporting to the die curler is not practical due to the tight nesting of a stack of blanked and formed shells.
Concerning the conveyance of parts between different shaping operations, means other than conveyor belt assemblies have been utilized, for example, pneumatic systems which generally comprise a large plenum and duct assembly. In these systems, parts such as bottles, cans, records, silicon waffers and the like are transported along a guide track overlying the ducts. The ducts have a plurality of openings disposed therein and the plenum provides a source of low pressure air which flows through the ducts and out the openings to convey the part from one area to another. This type of system poses numerous disadvantages when adapted to a shell press wherein a plurality of shells are formed simultaneously.
Recalling from above, shells are blanked and formed in groups of twelve, fourteen, or sixteen and in rows which are staggered relative to each other such that shells formed in one row overlap shells of adjacent rows. Therefore, it is desirable to transport alternate rows along different paths or tracks, which may be disposed relative to each other in a vertically adjacent manner. In such an arrangement, it is not practical or efficient to utilize the pneumatic systems of the prior art because of the large size of the ducts that provide air flow to the tracks. Such prior art systems would be difficult to adapt to a blanking and forming die station and a curling die station operated in the same shell press, and would also require an undue amount of material and space.
Examples of such pneumatic systems may be found in U.S. Pat. Nos. 3,874,740; 3,975,057; 3,953,076; 3,941,070; 3,293,414; and 3,645,581.